.btn{
    position: relative;
    display: inline-block;
    font-weight: $btn-font-weight;
    line-height: $btn-line-height;
    color:$body-color;
    white-space: nowrap;
    text-align: center;
    vertical-align: middle;
    background-image: none;
    border:$btn-border-width solid transparent;
    @include button-size($btn-padding-y,$btn-padding-x,$btn-font-size,$border-radius);
    box-shadow: $btn-box-shadow;
    cursor:pointer;
    transition: $btn-transition;
    &.disabled,//加了disabled类的
    &[disabled]{//加了disabled属性的
        cursor:not-allowed;
        opacity: $btn-disabled-opacity;
        box-shadow: none;
        > *{
            pointer-events: none;
        }
    }
}
.btn-lg{
    @include button-size($btn-padding-y-lg,$btn-padding-x-lg,$btn-font-size-lg,$border-radius-lg);
}
.btn-sm{
    @include button-size($btn-padding-y-sm,$btn-padding-x-sm,$btn-font-size-sm,$border-radius-sm);
}
.btn-primary{
    @include button-style($primary,$primary,$white)
}
.btn-danger{
    @include button-style($danger,$danger,$white)
}
.btn-default{
    @include button-style($white,$gray-400,$body-color,$white,$primary,$primary)
}
.btn-link{
    font-weight: $font-weight-normal;
    color:$btn-link-color;
    text-decoration: $link-decoration;
    box-shadow: none;
    &:hover{
        color:$btn-link-hover-color;
        text-decoration: $link-hover-decoration;
    }
    &:focus,
    &.focus{
        text-decoration: $link-hover-decoration;
        box-shadow:none;
    }
    &:disabled,
    &.disabled{
        color:$btn-link-disabled-color;
        pointer-events:none;
    }
}
